Measure radius of external arc, arc angle of measured surface should be larger than 90?
Resolution .0005″/0.01mm
Buttons: on/off, set, inch/mm, preset (+, -)
Automatic power off, move the digital unit to turn on power
Battery CR2032, Data outputMade of stainless steel
Supplied with pin gage for zero setting

3M 17528 Scotch-Brite Surface Conditioning Low Stretch Belt, SC-BL, A/O Very Fine, 1-1/2 in x 60 in, 7010292405
3M 19768, Utility Cloth Sheet 314D, 9 in x 11 in P180 J-weight, 7000000356
Insize 6140, DEPTH BASE ATTACHMENT, suitable for calipers with beam width (w) .630", 6928640303579
3M 97421, Aluminum Foil Tape 3380, Silver, 72 mm x 45 m, 3.25 mil, 7010375681 